Abstract:
Cinnamon is a major export spice crop in Sri Lanka. Rough bark and leaf blight diseases are fungal
infections that threaten most of the cinnamon cultivation in Sri Lanka. The common practice of
management of these diseases is the fungicide application. Food products grown under
agrochemical use rapidly losing favor with consumers, due to their known detrimental residue
effects on human health. Furthermore, studies shows that pesticide usage might irreversibly harm
the environment. As a result, organic food is becoming more popular in Sri Lanka, necessitating
the development of plant-based fungicides. Secondary metabolized phytochemicals with
antibacterial and antifungal properties are produced by plants. The antifungal activity of plant
extracts against the rough bark and leaf blight disease was evaluated in vitro in this study.
Pathogenic fungi were isolated from rough bark and leaf blight symptomatic cinnamon plants. The
screening of antifungal activity of ten different plant extracts prepared in aqueous and methanol
extracts of five plant species namely, Zingiber officinale (Ginger), Allium sativum (Garlic), Ocimum
sanctum (Tulsi), Azadirachta indica (Neem), and Tithonia diversifolia (Wild sunflower) were
assessed against Colletotrichum aenigma, Pestalotiopsis papuana and Colletotrichum sp. isolated
from rough bark infected cinnamon stems and fungi from leaf blight infected leaves. The three
isolated causative agents were identified based on ITS sequence similarity. The antifungal activity
of the ten different plant extracts was compared using the poison plate method. The results of this
study revealed that the growth of Colletotrichum sp. was completely inhibited by Z. officinale and
A. sativum. A. sativum and A. indica completely inhibited C. aenigma among other crude plant
extracts. Five crude plants extracts failed in completely inhibiting the P. papuana. All methanol
plant extracts showed 100% antifungal activity at 0.2 gmL-1 concentration, except O. sanctum
against C. aenigma. The value of minimum inhibitory concentration (MIC) of plant extracts was
determined and values ranged from 0.001- 0.3 gmL-1. This finding of the study concluded that
methanol extracts of Z. officinale, A. sativum, O. sanctum, A. indica, and T. diversifolia have an
antifungal effect over their fresh crude extract. This study makes the way for developing organic
fungicide with the added benefits of an environmentally safe and economically viable product.
